Fuel Efficient Five-Gear Rocket Engine Designed

Roland Piquepaille writes "Georgia Tech researchers have had a brilliant idea. Rocket engines used today to launch satellites run at maximum exhaust velocity until they reach orbit. For a car, this would be analog to stay all the time in first gear. So they have designed a new space rocket which works as it has a five-gear transmission system. This rocket engine uses 40 percent less fuel than current ones by running on solar power while in space and by fine-tuning exhaust velocity. But as it was designed with funds from the U.S. Air Force, military applications will be ready before civilian ones. Here is how this new rocket engine works."

Comments

Re:Solar?

[bky1701]

In *SPACE* you need very little. Ion drives work fine.

Say what?

[ottffssent]

IANAAE (aerospace engineer), but obviously this is only applicable if either

1. high-thrust mode is hugely less efficient than low-thrust mode, or
2. there is a considerable fuel cost to starting and/or stopping the motor.

If neither applies, then you would simply run the motor at high thrust for shorter periods of time, without the added expense of a low-thrust mode.

The article wasn't what you might call detail-oriented, but this is some sort of electric ion propulsion scheme, which achieves high specific impulse (~3000sec, accd. wikipedia) and so optimising for efficiency makes sense. But it's still an ion drive, so there'll be no takeoffs in its future. At least not takeoffs from anything with a gravitational well deeper than an asteroid.

So we have an article about a thing. Only the article doesn't say what it is or what it's good for. I think I'll keep getting my space news from not-ZDnet, thanks.

Soooo... it's another VASIMR?

[cbhacking]

Aside from the fact that the Variable Specific Impulse Magnetoplasma Rocket is designed for long-range spacecraft rather than satellites (and I think the difference is really only one of size) exactly how is it better/different? The VASIMR may actually be more versatile, and has quite a few advantages over standard ion designs (things like being completely electrodeless and containing its plasma propellent with EM fields so as to avoid corrosion). I'm all for improved rockets, and the general concept of the ion/plasma rocket is a good one, but it sounds like duplication of effort...

And now for something completely different...

[Richard Kirk]

I read the summary, and thought I understood it.

A conventional rocket motor chucks out lots of hot, ionized gas. In the lower atmosphere, this comes out as a long, thin flame. As the atmosphere gets thinner, the gas can fly out sideways. You have the paraboloidal bells at the base of the rocket with try an convert this sideways motion of the plasma into downward motion, so you get as much forward momentum as you can. However, the gas in the bells is colliding with itself as much as with the engine walls, so you will still get stuff spraying out sideways. What you would need is an impracticably huge bell shape so the gases thin out to the Knudsden regime before bounding specularly off the walls. However, you could steer the heavy positive ions backwards with a magnetic field pointing out of the back of the engine, perhaps backed up by additional coils once you are in space. It would be a bit like the hydrogen scoop on a Bussard ramjet, only not as big, and backwards.

Then I read the 'explanation'. Meh.